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These proceedings contain 27 papers, which are the peer-reviewed versions of presentations made at the International Association of Geodesy (IAG) symposium “Gravity, Geoid and Height Systems 2016” (GGHS2016). GGHS2016 was the first Joint international symposium organized by IAG Commission 2 “Gravity Field”, the International Gravity Field Service (IGFS) and the GGOS Focus Area “Unified Height System”. It took place in Thessaloniki, Greece, in September 19-23, 2016 at the premises of the Aristotle University of Thessaloniki. The symposium was organized by the Department of Geodesy and Surveying of the Aristotle University of Thessaloniki, which presently hosts the IGFS Central Bureau. The focus of the Symposium was on methods for observing, estimating and interpreting the Earth gravity field as well as its applications. GGHS2016 continued the long and successful history of IAG’s Commission 2 Symposia.
Masters Theses in the Pure and Applied Sciences was first conceived, published, and dis· seminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) *at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the ac· tivity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volume were handled by an international publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 20 (thesis year 1975) a total of 10,374 theses titles from 28 Canadian and 239 United States universities. We are sure that this broader base for theses titles reported will greatly enhance the value of this important annual reference work. The organization of Volume 20 is identical to that of past years. It consists of theses titles arranged by discipline and by university within each discipline.
This book will be based on the material of the lecture noties in several International Schools for the Determination and Use of the Geoid, organized by the International Geoid Serivice of the International Association of Geodesy. It consolidates, unifies, and streamlines this material in a unique way not covereed by the few other books that exist on this subjext. More specifically, the book presents (for the first time in a single volume) the theory and methodology of the most common technique used for precise determination of the geoid, including the computation of the marine geoid from satellite altimetry data. These are illustrated by specific examples and actual computations of local geoids. In addition, the book provides the fundamentals of estimating orthometric heights without spirit levelling, by properly combining a geoid with heights from GPS. Besides the geodectic and geophysical uses, this last application has made geoid computation methods very popular in recent years because the entire GPS and GIS user communities are interested in estimating geoid undulations in order to convert GPS heights to physically meaningful orthometric heights (elevations above mean sea level). The overall purpose of the book is, therefore, to provide the user community (academics, graduate students, geophysicists, engineers, oceanographers, GIS and GPS users, researchers) with a self-contained textbook, which will supply them with the complete roadmap of estimating geoid undulations, from the theoretical definitions and formulas to the available numerical methods and their implementation and the test in practice.
The point mass technique, which supplements a spherical harmonic expansion of the potential, allows short wavelength detail to be added to previously computed long wavelength geoidal features without distorting the latter. Recently, the AFGL short-arc approach to satellite altimetry has been modified to allow point mass adjustments. GEOS-3 altimeter residuals in the North Atlantic region were obtained from a first adjustment in terms of spherical harmonics and state vector parameters. A subsequent point mass adjustment was performed on these residuals to obtain the short wavelength geoid and gravity anomalies. Advantages of the point mass model stem from a flexible deployment of the new parameters (point mass magnitudes) in an area of interest that permits important computer savings when processing large amounts of satellite data in a local region.
We previously described (14,14) spherical-harmonic global adjustments of satellite altimetry using the AFGL short-arc technique supplemented with point masses to allow incorporation of short-wavelength geoidal detail. Recently, we have also investigated another technique to enhance short-wavelength detail: least squares collocation with noise. Both methods provide a means to determine a high resolution gravity field on a local, regional or global scale. Statistical comparisons of these two methods have been made in selected areas and the results tabulated.
The mathematical model for a simultaneous estimation of improved orbital parameters and an approximation of the earth's gravity field from range rate observations in an SST 'low-low' experiment is described. In a somewhat simplified model an error analysis for the estimation of geoid heights, geoid height differences 1 deg x 1 deg mean gravity anomalies is performed employing the least squares collocation method. Investigated is the dependence of the estimated parameters upon the measurement precision, the spatial configuration of the two satellites, the intersatellite distance, and the experiment altitude. In an optimal situation - assuming a range rate precision of + or - ten to the minus 6th power/ms, an intersatellite distance of 250 km, and an experiment altitude of 200 km - the estimated a posteriori std. dev. are + or - 0.9 m for point geoid heights, + or - 0.7 m for geoid height differences (point separation 150 km), and + or - 6 to 7 mgal for 1 deg x 1 deg mean gravity anomalies. These numbers compare very well with the results obtained from GEOS-3 altimetry for the seasurface topography. Unmodelled short-wavelength uncertainties in the orbit have thereby to be controlled down to 1 cm in radial direction, whereas the requirements for the control of long-wavelength error effects are moderate. (Author).
This book offers extensive information on the operation of gravimeters, including airborne, marine and terrestrial ones, and on the associated data processing methods such as optimal and adaptive filtering, smoothing, structural and parametric identification. Further, it describes specific features relating to the study of the gravitational field in remote areas of the Earth, with the necessary modifications of equipment and software for all-latitude applications. Findings from gravity studies in such remote areas are also presented. Advanced methods for studying the gravitational field, including those for simultaneous determination of gravity anomalies and deflection of the vertical are described and analyzed in detail. Gravity gradiometers and cold atom gravimeters are also covered. Last but not least, the book deals with the development of Earth’s gravity field models and their various applications, including map-aided navigation, with a special attention to model accuracy estimation. Gathering research findings and best practice recommendations relating to Earth’s gravity field measurements, collected by a team of researchers and professionals, the book offers a unique guide for engineers, scientists and graduate students dealing with terrestrial, marine and airborne gravimetry. It will also help other specialists involved in developing and using navigation systems in practice, including designers of gravimetric equipment and navigators.